U.S. Pat. No. 4,748,239 to Floyd et al. discloses compounds having the general formula ##STR5## These compounds are vasodilators and therefore are especially useful as antihypertensive agents.
A key intermediate in the preparation of compounds of formula A and other such compounds, is the compound having the formula ##STR6## being the cis(+) isomer. This is so because the cis(+) isomers of compounds of formula A exhibit the greatest vasodilating activity. Several routes for providing the desired resolved products of formula A are outlined in the above-mentioned Floyd et al. patent.